In many cases, tooth replacements are attached in the mouth of a patient with the aid of an implant. In these cases, the implant is typically provided with a so-called abutment after it has been inserted, said abutment being connected with the implant positively, for instance by configuring the surfaces of implant and abutment which face one another non-circularly. Then, the attachment itself is effected by means of an abutment screw which passes through the abutment. For this purpose, an upper area of the abutment is configured as a tubular portion, whose internal diameter is sufficient for receiving the abutment screw. The abutment screw is supported slightly below this tubular portion on a supporting area which is slightly conical in most cases whose internal diameter is smaller than the diameter of the head of the abutment screw but through which the shank and the thread of the abutment screw fit. Then, the implant comprises an internal thread for threaded engagement with the thread of the abutment screw, in a way known per se.
Subsequent to the attachment of the abutment to the implant a dental structure is attached on the abutment. For this purpose, the tubular portion or the upper area of the abutment is slightly conical on the outside in most cases and fits positively into a corresponding recess in the dental structure.
Solutions of this type have been used for approximately 30 years; by way of example, it is referred to DE 32 41 963 C1 or GB 2 119 258 A, in this respect.
However, especially with the solution according to the latter reference there is the problem that the rotary position of the dental structure relative to the implant is not determined or not clearly determined. In this connection, a better and slightly more recent solution may be taken from U.S. Pat. No. 5,782,918 A1 which shows an anti-rotation mechanism in the form of a flattening of the tubular portion of the abutment and in this respect realizes an anti-rotation mechanism between implant and dental structure.
In this solution, only one single size or height of the abutment is provided which is selected to have such a small size that even more compact dental structures completely cover the tubular portion.
In order to improve the handling and in particular also the process sequence in the secure attachment of the suprastructure on the abutment various auxiliary elements have already been suggested.
In this respect, it has been suggested to push a type of hose having a wall thickness of, for instance, 0.5 mm, onto the tubular portion of the abutment without further ado, in order to ensure that a sufficient adhesive gap is provided later on. However, due to the elasticity of the hose no uniform—and at the same time low—thickness of the adhesive gap can be realized.
Furthermore, pre-fabricated auxiliary elements have also been suggested in which an anti-rotation mechanism is ensured by means of a projection pointing to the outside. However, with this type of anti-rotation protection there are problems in the realization of bridges which are basically self-adjusting in terms of the angular position such that an anti-rotation protection of this type is disturbing.
A further problem are the undercuts and retention grooves which are provided in this respect and which generate comparatively large adhesive joints. In this way, adhesiveness is reduced comparatively strongly in these areas, especially as this may lead in other areas to material thicknesses being fallen below, particularly in the marginal area of the restoration, on the other hand.